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List:       openembedded-core
Subject:    [OE-core] [PATCH 4/5] libav: upgrade to 9.18
From:       rep.dot.nop () gmail ! com (Bernhard Reutner-Fischer)
Date:       2015-05-30 13:17:39
Message-ID: 5664EFD5-15CB-4772-95FB-1DE7232A62D1 () gmail ! com
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On May 30, 2015 12:24:30 AM GMT+02:00, Phil Blundell <pb at pbcl.net> wrote:
> On Fri, 2015-05-29 at 16:28 +0100, Paul Eggleton wrote:
> > Just for background, the reason I disabled the textrel check for x86
> in 
> > libav.inc was that I was able to determine based on quick research
> that 
> > upstream deliberately doesn't enable -fPIC for x86 (32-bit) because
> apparently 
> > it doesn't really work there. I honestly didn't check what the
> situation was 
> > on 32-bit ARM; I probably should have done that at the time.
> 
> PIC is particularly problematic on x86 because it ties up %ebx.  This
> represents 25% of the available general purpose registers which can
> cause a measurable performance loss because of increased spilling, and

Note that the situation improved with gcc-5 for some cases though.

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54232
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47602
https://software.intel.com/en-us/blogs/2014/12/26/new-optimizations-for-x86-in-upcoming-gcc-50-32bit-pic-mode


Cheers,


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